Truth Tables in PBP

[ecoli-557]

Hey Everyone-
I have queried this forum and have not found much in this area.
I am attempting to 'clone' a logic board which cannot be purchased any longer and is no longer supported for a client. I have all the inputs and results for outputs but my main question is has anyone used a micro in place of logic gates?
I have tried a couple of ways to provide inputs using IF/THEN type statements but it seems clunky and verbose.
Almost think there may be a way to map inputs to EEPROM locations and read data straight out........
Its pretty small; only 4 inputs and 3 outputs and a timing function of 2 seconds.
Curious if anyone has tried to do this?
Thanks in advance for any insight!

[richard]

four inputs
could be
a var portb.0
b var portb.2
c var porta.3
d var portc.3

outputs could be
e var portc.0
f var portc.1
g var portc.2

formula e = a or b and c ,f= d and c or b, g = b and c and d

code
e = (a or b)and c
f= (d and c) or b
g=(b and c)and d

[Archangel]

Select case cleans up on multiple if/then applications, on goto and on gosub work too.

[pedja089]

If you need fast response you can create tables using arrays.
For 4 bit system you have 16 different states, so you create array which hold data for output for every 16 states. And use 4 bits of ports for inputs, and outpust, eg portb0 to Portb3 is inputs, portA0 to 3 are outputs.
TruthTable var byte[16] BANKA'So pbp doesn't need to put banksel after each command
TruthTable[0]=%00001111
TruthTable[1]=%00001100
etc...
TruthTable[15]=%00001111
TRIS...
ANSEL
ETC..
Tmp Var byte BANKA
Main:
Tmp=portb & %00001111
porta=TruthTable[Tmp]
goto Main
This will give almost fastest response for given clock speed.
If you grounded upper nibble, this give you fastest possible responese
Main:
porta=TruthTable[portb]
goto Main
If speed isn't critical you can assign bits to Tmp variable from any pin...

[ecoli-557]

Thanks Guys!
While all are better than what I was playing with, I like the array scheme. I just don't do enough arrays to keep them front and center in my head.
Unfortunately, I didn't have the presence of mind to neatly stack the inputs into a nibble on a port..... using A0, A1, A4, and A5 on a 16F616
I do understand the philosophy, but there is one wrinkle; there are 2 cases in which I need to a pin high, time out for 2 sec and then go low. If the condition on the inputs pins stays the same, the timed pin just stays high.
I even used DT's instant interrupts (so cool) to time the pin but that didn't seem to work.
This should be so easy, but I am missing something and its probably so visible that I can't see it!
What I get when I test my primitive code is the LEDs flash (I use them for debugging) and the timed pin never times out UNTIL the input condition changes. Snippit below:

          if command=1 and dpi=0 and bolt=1 and deadlck=1 then                 
                t1=0 : t2=0 : t3=1     'leds
                if tflag=1 then Main1X    'been here before so step around
                unlock=0
                unsecure=0
                lock=1     'Turn ON sol
                t1=0 : t2=1 : t3=0
                pause 2000     'wait 2 sec
                t1=0 : t2=1 : t1=1
                lock=0     'Turn OFF sol                
                tflag=1     'We did it so set flag
                t1=1 : t2=0 : t3=0
Main1X:         t1=1 : t2=0 : t3=1
                unlock=0
                unsecure=0
          endif

[EarlyBird2]

t2 is the timed pin?

is tflag being reset to 0 elsewhere in your code?

Like you I see no problem with this snippet.

[Archangel]

Could be RMW issue if those T# are on same port, better in that case to change them all at once like PortB=%00000100 PortB = %00000011

[EarlyBird2]

Thanks Guys!
While all are better than what I was playing with, I like the array scheme. I just don't do enough arrays to keep them front and center in my head.
Unfortunately, I didn't have the presence of mind to neatly stack the inputs into a nibble on a port..... using A0, A1, A4, and A5 on a 16F616

There are ways around this.

One is to use maths

myvar=PORTA.0+PORTA.1*2+PORTA.4*4+PORTA.5*8

Another way is bit manipulation

myvar=PORTA & %00110011 ' select the input pins
myvar=(myvar & %00000011) + (myvar & %00110000)>>2 'selects A0,A1 then selects A4 and A5 moves then to A2 and A3 and adds to A0,A1

Another way is to set Aliases for the pins which relate to myvar. I will let you look into that one and I am sure there must be other workarounds.

Then myvar can be used in LOOKUP to set an output pattern or used in SELECT CASE or IF THEN, the choice is yours.

[ecoli-557]

Thanks Guys!
I thought there had to be another way....
BTW, it WAS a bug in my code that kept me from the timing sequence. I just tripped out all the code but the one conditional area - code worked like I thought it should.
Then with the entire code back, I systematically remarked all the other places in the code where I zeroed the TFLAG bit var which was in all the other conditionals until it passed the var the way it should.
Turns out you actually can not type using all thumbs! I had mistyped and it was staring me in the face.......

Now that it actually works, its now going to be a learning experience and a life lesson to try these other ways so I may help someone down the road.
Starting with arrays and trying the bit manipulation schemes.......

Thanks and Regards.
Steve